1. Field of the Invention
The present invention relates to a rescue device whose power efficiency is improved with the use of an Auto Landing of Power failure device (Hereinafter, referred to as an ALP device), and in particular to an ALP device capable of providing a function of an active filter during a normal power supply with the power efficiency of a control panel improved, while still providing its own function when a power failure occurs.
2. Description of the Related Art
In general, an elevator system includes an ALP device to accomplish a rescue operation so as to rescue a plurality of passengers locked in an elevator car which is abruptly stopped due to a power failure.
When a power failure occurs, the ALP device supplies its battery voltage to the control panel after adjustment of its battery voltage to a predetermined level which is appropriate to an input terminal of the control panel. However, the ALP device is not operating unless the power source fails or is malfunctioning.
FIG. 1 shows the construction of a control panel 1A and the ALP device 1B which are included in a rescue device. Referring to FIG. 1, the control panel 1A comprises an AC/DC converter 3 for converting an AC power transmitted from a three-phase AC voltage source 1 via contacts 2 which is closed when the power is supplied to elevator devices; a capacitor 4 acting as a smoothing circuit for decreasing the ripple of the DC power outputted from the AC/DC converter 3; an inverter 7 for converting the DC voltage across the capacitor to the three-phase AC voltage with a variable voltage VV and a variable frequency VF; a current ampere meter 8 for reading the output current of the inverter; an induction motor 9 for supplying the power to an elevator cage 12; a speed meter 14 for reading the angular speed of the rotating induction motor; a load detector 15 for detecting the load of the elevator car 12; a central processing unit (hereinafter, referred to as a CPU) 16 for controlling the operation of the inverter 7 so as to make the induction motor to rotate at a target speed upon receipt of output signals of the ampere meter 8, the speed meter 14, and the load detector 15, and for controlling the operation of an element 6 to be conducted resulting in that the power generated from the induction motor when the induction motor starts to rotate in regenerative power domain can be consumed by passing through the resistor 5; and a voltage transformer 17 for supplying an appropriate voltage to the CPU with its fixed turn ratio.
The ALP device 1B comprises a battery 24 for supplying a stand-by DC power of a predetermined level to the system; a capacitor 23 for smoothing the ripples of the DC voltage outputted from the battery; a stand-by inverter 22 for converting the DC voltage across the capacitor to the three-phase AC voltage with the variable voltage VV, and variable frequency VF; an ampere meter 21 for reading the output current of the stand-by inverter; a reactor 20 for smoothing the output current provided to the transformer 18 from the stand-by inverter; a filter 19 for filtering the output voltage provided to the control panel 1A from the inverter 22 across the reactor; a voltage transformer 18 for transforming the output voltage of the inverter 22 to an appropriate level for the CPU 1A; an AC voltmeter 25 for reading the AC voltage from the filter; an automatic rescue mode controller 26 for controlling to activate the stand-by inverter 22 upon receipt of the output signals of the ampere meter 21 and the AC voltmeter 25. Here, the reference numerals 10, 11, and 13 respectively denote a traction machine, a brake, and a counterweight.
The operation of the rescue device as constructed above will be described with reference to FIGS. 1 and 2. When the three-phase AC voltage source is normally supplying the power, the contacts 2 is in an ON-state so that the voltage of the three-phase AC voltage of a predetermined level is supplied through contact 2 and the voltage transformer to the CPU 16. The voltage of the three-phase voltage is also supplied through the converter 3 and the capacitor 4 to the inverter 7.
The inverter 7 then controls the torque and the rotation number of the induction motor 9 by outputting the three-phase AC power to the induction motor in accordance with an AC voltage signal inputted from the CPU.
The CPU 16 also determines whether or not the regenerative power is generated from the induction motor. If determined that the regenerative power is generated, the CPU outputs a control signal to the element 6 such that the element is conducting, causing the regenerative power to be transmitted through the element and then to be consumed through a resistor 5.
However, if the three-phase AC voltage, namely the normal power source is failed or malfunctioning, the contacts is in an OFF-state. At this time, the DC voltage from the battery 24 is transmitted to the stand-by inverter 22. The stand-by inverter 22 converts the DC voltage across the capacitor 23 to the three-phase AC voltage with the variable voltage and variable frequency upon receipt of the signal from the CPU. The reactor 20 smooths the ripple of the output voltage of the stand-by inverter and transmits the smoothed voltage to the filter. The filter 19 filters the input voltage, and transmits the filtered voltage to the voltage transformer 18. The voltage transformer 18 transforms the input voltage to a predetermined level. On the other hand, the AC voltmeter 25 reads the voltage from the filter, and transmits it to the rescue mode controller 26. The transformer 18 provides its output voltage to the converter 3 disposed in the control panel 1A.
The CPU 16 therefore is operable at the same condition even when the power failure occurs. However, the CPU recognizes that the power is supplied not from the inverter 7 but from the stand-by inverter 22, so that the CPU sets the system with the rescue mode and is operating accordingly to rescue the passengers locked in the elevator car.
The CPU also sends the control signal to make the element 6 conducting so that the regenerative power generated from the induction motor 9 can be consumed and eliminated by passing through the conducting element 6 and then the resistor 5.
However, when the induction motor 9 is activated by the converter 3 and the inverter 7 to shift the elevator car 12 to the destination floor landing in response to a car call signal or a hall call signal generated by the passenger(s), the current of the converter 3 will be a pulse type as shown in the FIG. 2b.
When the current pulse reversely passes to the three-phase AC voltage 1, the total power efficiency cos .phi. can be expressed with the power efficiency of the fundamental wave cos .phi..sub.1 and the distortion ratio .mu. as in the following equations 1 and 2. ##EQU1## (Here, .phi. and .phi..sub.1 are phase differences between the current and the voltage of the fundamental wave and the total wave including the fundamental wave and the harmonic wave.)
As can be seen in the equations 1 and 2, the total power efficiency becomes degraded (normally in the range of 0.6.about.0.75) when the distortion ratio of the current is getting worse. Accordingly, the conventional rescue device suffers from the disadvantages in that the power consumption and the complexity of the input terminal of the control panel are getting increased, and a serious harmonic wave distortion appears at the input terminal.
The conventional rescue device also suffers from a further disadvantage that the ALP device becomes operable only when the power failure occurs, so that the efficiency of the ALP device is low compared to its price.